James, what is your past experience? Are you set on 35mm focal length or are you looking for ideas about focal length as well? I like Rover's suggestion that you consider 40mm as one of your options. If you are going to have just one lens, that's a good length to pick.
If you decide to buy the 35 Summicron, there is a big difference in weight between black & chrome. Chrome is 4 oz. heavier - an increase of almost 50% in lens weight. Since you said you want a lightweight kit, I'd go with black. Optics are the same - excellent.
You can get even lighter by getting either of the Voigtlander 35/2.5 lenses. The Pancake & the Classic are the same weight, i.e. about half as heavy as the black Summicron (or 4 oz. lighter). The Classic is a little longer but has a more classic, elegant look & is still quite compact. I've never heard anyone complain about the optical quality of either of these 2 lenses & many people have sung their praises. The Classic needs an adaptor to be mounted on an R2/3, which is $33 for a generic at Cameraquest - but it's still $70 cheaper than the Pancake even with the additional cost of the adaptor. It's a real bargain right now. The Summicron is only 2/3 stop faster - not a lot to sacrifice for the savings in size & weight. I rarely shoot at f/2, so it's no sacrifice for me. If you need the extra speed,one of today's great fast films is a cheap solution.
If you're likely to be sticking with a single lens, a good choice would be a Bessa R with the 35/2.5 Classic for as little as $399 from Cameraquest on a close-out sale. It will not accept M-mount lenses, so if you get hooked, you might some day trade up to an M-mount body. Or you might not. Mechanically it's the same as the R2, has the same viewfinder & same rangefinder, & it has the additional feature of a self-timer, which the R2 does not. And you can use 90% of the Voigtlander lenses on this body. It's a great way to get started with a rangefinder & you can always sell the body if you eventually want a different one or keep it as a second body. This set-up will also come with a year's warranty vs. a used R2 which will not. And you'll have $1000 left in your pocket!
IMO, you'd do best with a single lens right now unless you already know of other focal lengths that you need. If you do not, shoot with the 35mm lens for a while & then decide what else you need to go with it.
Happy shopping!
